Flame-holder of the eliminable fluid-screen type



J 1964 J. H. BERTIN ETAL 3,136,124

FLAME-HOLDER OF THE ELIMINABLE FLUID-SCREEN TYPE 3 Sheets-Sheet 1 Filed May 11, 1956 INVENTo TEAM HIBERTIN J.M.$ mmu a/WMM ATTO ENE Y3 J 1964 J. H. BERTIN ETAL 3,

FLAME-HOLDER OF THE ELIMINABLE FLUID-SCREEN TYPE Filed May 11, 1956 3 SheetsSheet 2 \NVENTO'RS JEAN ".BERTIN BJKMSALM N 11 MM+4JM ATToR NE Y5 June 9, 1964 .1. H. BERTIN ETAL 3,135,124

FLAMEHOLDER OF THE ELIMINABLE FLUID-SCREEN TYPE Filed May 11, 1956 3 Sheets-Sheet 3 \NVENTORS EAN .BERTIN Z -MSALMoN Mm 60-4, M rm,

ATTORNEYS United States Patent Nationale dEtude et de Construction de Moteurs dAviatiou, Paris, France, a French company Filed May 11, 1956, Ser. No. 5843369 Claims priority, application France May 13,

2 Claims. (Cl. 6039.72)

In the US. patent application Ser. No. 379,663, filed September 11, 1953, relating to combustion arrangements in which a fuel is to be burned inside a stream of gas flowing at an appreciable speed, is described devices for stabilising the combustion, comprising means adapted to ensure the formation of a fluid screen in the jet of gas, on the upstream side of the zone in which the flame is to be produced. This screen produces a wake zone in which there is turbulence, and in which the flame can be fixed and stabilised, and it does not have the drawbacks of the solid screens previously employed for the same purpose.

It has been observed that in certain combustion chambers or exhaust nozzles, especially in the post-combustion chambers of reaction units, the combustion gives rise to appreciable vibrations which are liable to lead rapidly to fracture, and this is true whatever may be the type of stabilisation screens employed.

The present application has for its object arrangements of fluid screens in accordance with the main patent, which enable vibrations to be eliminated.

To this end, the nozzles which produce the fluid screens are formed in at least two different zones following each other at a suitable distance in the direction of flow of the main jet, in the centre of the combustion chamber or the exhaust nozzle.

In each of these zones, the'distribution of the auxiliary fluid which forms the screen may be uniform, the screen being thus associated with the whole transverse section of the combustion chamber. The blowing or injection device for the auxiliary fluid will then comprise either a continuous nozzle such as a slot, or one or a number of series of holes uniformly spaced apart.

It is also possible to provide a non-continuous or nonuniform distribution of the auxiliary fluid in each of the zones, by then forming the nozzles preferably in such v manner that the gas flowing in the combustion chamber, which passes into a zone which has no nozzles or a small number of nozzles, then passes into a sector of another zone provided with nozzles or having a large number 1 of nozzles,

The description which follows below with reference to the attached drawings (which are given by way of exampleonly and not in any sense by way of limitation) will make it quite clear how the invention may be carried into effect, the special features which are brought out either in the text or in the drawings, being understood to form a part of the said invention.

FIGS. 1 to 4 are diagrammatic views in perspective,

with portions broken away, of various forms of embodiment of the invention as applied to an after-burning exhaust nozzle of a reaction unit.

FIG. 5 is a view of a detail in cross-section'along a plane which passes through the axis of the exhaust nozzle.

FIG. 6 is an axial cross-section of a post-combustion discharge nozzle in which the auxiliary fluid which supplies the screens provides in addition a means of cooling the supporting member of the nozzles.

The drawings are concerned with the especially advantageous case in which the nozzles which serve to produce the fluid screens are provided on a support 1 which exsolution,

40 been found that by 3,136,124 Patented June 9, 1964 lCC tends along the axis of the combustion chamber 2. This support 1 exists in general in the after-burning exhaust nozzles of reaction units, in which it forms, on the downstream side of the turbine (of which some of the blades have been shown at 3 in FIG. 1), an aerodynamic cowling or trailing-cone which assists the flow of the gases discharged from the turbine towards the outlet orifice of the exhaust nozzle. This arrangement, although it may be of great advantage, is not however the only possible and the nozzles could be arranged in other ways, for example on the internal wall of the exhaust nozzle, or on rings or any other kind of support specially provided in the combustion chamber.

FIG. 1 shows a first arrangement in accordance with the present addition, in which the nozzles are provided on the support 1, downstream with respect to the fuel injecting heads 1,;, in two planes at right angles to the axis A-A of the exhaust nozzle, and the intersections of which with this axis are at P1, P2 at a certain distance apart L. In each of these planes (the word plane not being used here, ofcourse, in its strict geometric sense of a surface having no thickness), there are three rings of nozzles formed by small holes 4 drilled in the wall of the support 1, and supplied with auxiliary fluid, for example with air derived from the compressor of the reaction unit, by suitable annular collectors 5 (see FIG. 5) provided in the support 1. The holes may be directed insuch manner that the jets f are discharged at right angles to the direction F of the main jet inside the exhaust nozzle. They may also be inclined towards the upstream side or the downstream side of the main jet. They may form true expansion nozzles which impart to the auxiliary fluid the maximum momentum in order to facilitate the penetration of this fluid into the main jet, by having a certain length of tubular wall 6 (see FIG. 5) fixed to the supportl.

FIG. '1 shows an arrangement in which the holes are equally distributed in each of the planes P1, P2. It has giving the distance L between these planes a suitable value, which can be determined by experiment for each type of combustion chamber, it is possible to eliminate the vibrations, this fact being no doubt explained by an action on the propagation of the pressure waves which are produced during the combustion.

At least two successive flame-fronts are created at different places, and this gives rise to the super-position of at least two series of vibrations which may be caused to act in opposition and to annul their total effect by a suitable location of the origin of the flame-fronts.

It is of course possible toprovide more than two planes with equal or unequal spaces between the successive planes. The angle of orientation of the nozzles may be different from one plane to another.

The form of embodiment of FIG. 2 differs from that preceding by the fact that the distribution of the nozzles in each of the planes P1, P2, is non-continuous. In the plane PI for example, there are two opposite sectors having an angle a at the centre, covered by the holes 4,

gered by sectors from one plane to the other may be more uniform, it is preferable to give the sectors a slight overlap, of 10 for example.

It is advisable to note that, in certain reaction units, the residual rotation of the jet of gas at the outlet of the turbine may tend to modify the angular displacement of the sectors of holes from one plane to the other. If the jet even makes one quarter of a revolution between the (.11 plane P1 and the plane P2, the sectors located in these planes and supposed to include an angle of 90 at the centre should not be displaced at all, but should be located geometrically one behind the other in order to be associated with all the streams of fluid in their helical movement.

In the alternative form shown in FIG. 3, the nozzles are arranged in successive sectors following the parts of a spiral. When moving round the support 1, there are successively encountered the helical sector S, which includes an angle al at the centre, the sector s making anangle a2, the sector .9 making an angle a3 and the sector .9 having an angle a4.

The end f of the sector s is located on the same generator of the support 1 or the same meridian of this support as the origin of the sector s and so on, but with a suitable distance between and 0 along this generator or this meridian. As indicated above, it may however be an advantage'to give the sectors a slight overlap in projection on a plane at right angles to the axis of the exhaust nozzle, such as for example.

In the alternative form of embodiment shown in FIG. 4, cert'ain sectors such as s s instead of not being provided with any blowing orifices, have only a small number. These sectors being opposite the sectors such as s' 8' of the other plane in which there are a number of rows of orifices, the density of the orifices varying preferably progressively from one sector to the next adjacent sector, as shown in'the drawing.

It will be noted that in the embodiments described above, the support 1, instead of having a conical or ogeval form, as is known and usual, has an intermediate portion i which is cylindrical or only slightly conical, and 'on which the blowing nozzles areformed, so that the relative penetration of the auxiliary jets into the main jets is substantially the same for all'the nozzles, in spite of them being spaced apart along the length of the support L. In the same zone, the nozzles may be given the same or different directions of inclination.

FIG. 6 shows the manner in which the circulation of V the air may be'arranged to supply the fluid screens, in

such manner as to ensure a cooling effect of the wall of the support 1. The air which 'is derived for example from the compressor of the reactor, passes through the conduit "8 into a chamber 9 located at the rear of the support '1 i and passes from thence towards the rings of orifices 4,

whilst circulating in an annular passage 10 comprised 4:? between the wall of the support 1 and an internal added wall 11. Cooling of the wall of the support 1 is thus effectively obtained.

hall the forms of embodiment described above, the whole or part of the'fuel which is to be burned in the combustion chamber may be injected into the air which supplies all or part of the fluid screens.

What we claim is:

1. In a combustion chamber traversed by a high speed fluid vein, a flame stabilizer of the retractable fluid screen type comprising a plurality of radially directed nozzles adapted to produce, when fed with fluid under pressure, transverse jets in the said chamber, said nozzles being concentrated in at least two zones staggered in the direction of flow of the fluid vein, and being concentrated within said zones along angularly staggered sectors in such a manner that a sector with a high density of nozzles located in one zone is not situated behind, with respect to the fluid vein, a sector with a high density of nozzles in the other zone, the nozzles within each zone'bein arranged along part of a helix.

2. In a combustion chamber traversed by a high speed fluid vein, a flame stabilizer of the retractable fluid screen type comprising a plurality of radially directed nozzles adapted to produce, when fed with fluid under pressure, transverse jets in the said chamber, said nozzles being concentrated in at least two zones staggered in the direction of flow of the fluid vein, and being concentrated within said zones along angularly staggered sectors in such a. manner that a sector with a high density of nozzles located in one zone is not situated behind, with respect to the fluid vein, a sector with a high density of nozzles in the other zone, the combustion chamber being annular and limited inside by a wall which has two strongly tapered parts separated by a cylindrical part, the nozzles being arranged on said cylindrical part near the ends.

References Qited the file of this patent UNITED STATES PATENTS 

1. IN A COMBUSTION CHAMBER TRAVERSED BY A HIGH SPEED FLUID VEIN, A FLAME STABILIZER OF THE RETRACTABLE FLUID SCREEN TYPE COMPRISING A PLURALITY OF RADIALLY DIRECTED NOZZLES ADAPTED TO PRODUCE, WHEN FED WITH FLUID UNDER PRESSURE, TRANSVERSE JETS IN THE SAID CHAMBER, SAID NOZZLES BEING CONCENTRATED IN AT LEAST TWO ZONES STAGGED IN THE DIRECTIONS OF FLOW OF THE FLUID VEIN, AND BEING CONCENTRATED WITHIN SAID ZONES ALONG ANGULARLY STAGGED SECTORS IN SUCH A MANNER THAT A SECTOR WITH A HIGH DENSITY OF NOZZLES LOCATED IN ONE ZONE IS NOT SITUATED BEHIND, WITH RESPECT TO THE FLUID VEIN, A SECTOR WITH A HIGH DENSITY OF NOZZLES IN THE OTHER ZONE, THE NOZZLES WITHIN EACH ZONE BEING ARRANGED ALONG PART OF A HELIX. 